SAFETY WINDOW

Abstract: A safety window is designed as a glass sheet unit (10) comprising at least two spaced-apart successive laminated glass panels (11, 12). Each laminated glass panel comprises at least two glass sheets (15, 16, 21-23) and three polycarbonate sheets (17-19, 24-26). These sheets are so laminated with each other that the two outer surfaces of the laminated glass panels (11, 12) are formed of glass sheets (15, 16, 21, 23).

Description: SAFETY WINDOW This invention relates to a safety window which may be used as display window in a showcase or as bullet-proof window in a bank or elsewhere where security requirements are high. In order to assess the capacity of safety windows to withstand mechanical working, the Swedish Theft-Prevention Association tests safety windows according to Swedish Standards SS 3492, 2nd Ed., Test with Hand Tools, Sec. 5, to provide a basis for a specification of the requirements, Sec. 4.1, 4th paragraph. In the test, use is made of a sledge, a chisel retainer, a pointed chisel, a drilling machine as well as other tools stated in the standard specification, the purpose being to make a standard hole measuring 100 x 100 mm. When it comes to testing bullet proofness, there are no such standard speci¬ fications. However, a common method consists in firing at the safety windows from a distance of 10 m with powerful firearms, such as an automatic carbine of Ak4 type (7.62 mm live cartridge 10, muzzle velocity 820 m/sec.) or Ak5 type (5.56 mm live cartridge 5, muzzle velocity 930 m/sec). In order that a safety window should pass the hand tool test, it has to take at least 10 min. to make a standard hole measuring 100 x 100 mm therein. As to the bullet-proofness require- ment, the bullets from such powerful firearms as are mentioned above should not be able to penetrate the safety window. One widely-used bullet-proof window is made up of five lami¬ nated glass panels (SE-B-437,729) or eight laminated glass panels (VEGLA of the make St Gobain), such that the whole assembly has a thickness of 39 mm. Although such safety windows are able to with¬ stand the fire from powerful firearms, they have poor resistance to working by hand tools (often 3.5 min. in tests of the VEGLA window in accordance with the above standard specification). The rather thick VEGLA window in addition has the disadvantage of a green-toned appearance due to the considerable thickness of the glass. The greater the number of glass panels or the greater the total thickness, the greener the safety window. In order to master the problem of green toning and other optical errors, such as Newton's rings, in safety windows composed of several glass sheets that have been joined together, SE-B-358,466 provides safety windows which are designed as glass sheet units made up of a number of glass and polycarbonate sheets. Thus, the SE specifica¬ tion describes windows in which glass and polycarbonate sheets are arranged in alternate fashion, either in direct contact, with or without a binder, or at a distance from one another. Although such a window is able to withstand a certain degree of firing, it has an extremely low resistance to mechanical working by hand tools. Thus, the outer panes or sheets, which consist of a single glass layer, are easily crushed, e.g. with the aid of a sledge, and it is then fairly easy to make holes in the centrally located polycarbonate sheets, which have low resistance to cutting and drilling. In addition, there is a consider- able risk of condensation in the glass sheet unit when the polycarbo¬ nate sheets are separated and exposed to air. Naturally, condensation has an adverse effect on the optical properties of the assembly. Thus, none of the prior-art constructions combines good optical properties, good resistance to mechanical working by hand tools and good resistance to effective fire from heavy firearms. Naturally, there is a demand for such a safety window, since the one type of attack does not exclude the other. In banks, for instance, the need for such higher security has, regrettably enough, increased. In addition, the safety windows used in banks and the like have to exhibit good optical properties and render shapes and also colours as naturally as pos¬ sible. One object of the invention is, therefore, to provide a safety win¬ dow which not only meets the somewhat contradictory requirements on high resistance to mechanical working by hand tools, high resis- tance to firing also with heavy firearms, and minimum optical distor¬ tion or undesirable colour toning preventing a natural colour rendi¬ tion. This and other objects of the invention are met by a safety win¬ dow as defined in appended claim 1 Especially preferred embodiments of the invention are stated in the subclaims. To put it briefly, the inventive solution to the problems with prior-art safety windows is based on the insight that the safety win- dow should be formed of at least two spaced-apart successive lami¬ nated glass sheet panels, each comprising at least two glass sheets and three polycarbonate sheets, which are so laminated with one another that the two outer surfaces of each laminated glass panel are formed of glass sheets. Apart from offering much better protection against burglary with the aid of hand tools and much better protection against firing also with heavy firearms, the safety window according to the invention has the considerable advantage of a lower total weight than many prior-art bullet-proof windows, especially those made of glass material only. The invention will now be described in more detail with refe¬ rence to the accompanying drawing, which illustrates an embodiment of a safety window according to the invention and more precisely is a sectional view of an edge portion of the window and its attachment. The illustrated embodiment of a safety window is designed as a glass sheet unit 10, in which two laminated glass panels 11, 12 are spaced apart by a circumferential spacer 14, e.g. of aluminium, so that there is formed an air gap 13. The spacer 14 may be composed of hollow-section strips and contain a drying agent, especially if the glass sheet unit 10 is designed as a thermopane assembly, i.e. if the space between the two laminated glass panels 11, 12 is hermetically sealed. Each of the laminated glass panels 11, 12 comprises several glass and polycarbonate sheets. In this embodiment, the outer laminated glass panel 11 is form¬ ed of two external layers 15, 16 of glass material and three interme¬ diate layers 17, 18, 19 of polycarbonate material. The different sheets or layers are joined with one another over their entire mutually facing sides. To this end, epoxy adhesive may be used. However, use is preferably made of a thin polyurethane film which, by low heating of the supe ^sed glass and polycarbonate sheets, is anchored in the sheets t. oind them together. Polyurethane film has the advantage of acting as a dampening cushion between adjoining sheets and thus contributes to increase the resistance to mechanical working and firing. Also other types of binder layers, e.g. of polyvinyl butyrate, may be used. However, this type of binder layer provides slightly weaker adhesion between the sheets than do poly- urethane films and epoxy layers but is, for many purposes, fully satis¬ factory. In the illustrated embodiment, a binder layer 20 of polyvinyl butyrate or polyurethane is arranged between the outer glass sheet 15 and the intermediate polycarbonate sheet 17 closest thereto. The other sheets are laminated with each other by layers of epoxy adhesive. The inner laminated glass panel 12 consists of three glass sheets 21, 22, 23 and three polycarbonate sheets 24, 25, 26. All these sheets are laminated with each other by some suitable adhesive, espe¬ cially an epoxy adhesive. In the illustrated embodiment, the inner laminated glass panel 12 is not provided with any dampening layer. Should one, however, wish to increase the resistance to impacts and bullets, a dampening layer equivalent to the binder layer 20 may be inserted in the inner laminated glass panel 12 as well. This design of the safety window results in very high resistance to firing and mechanical working, e.g. when there is an attempted burglary, since the air gap 13 between the two laminated glass panels 11, 12 makes it much more difficult to make holes in the safety win- dow with the aid of cutting tools. The air gap further enhances the capacity of the safety window to resist firing, since any bullets passing through the first or outer laminated glass panel 11 will be deformed, thus having lost part of their penetration power. Thus, the air gap 13 renders penetration into the inner laminated glass panel 12 more difficult. The safety window can be attached in many ways. The drawing shows one advantageous attachment arrangement. Here, a mounting section 27 of standard steel or stainless steel is fixed in a surrounding building structure 28. A plate 29 of high- strength steel is fixed at the back of the mounting section and serves as protection against the penetration of bullets. In the mounting section 27, there is provided a torsionally rigid frame section 30, which is designed as an extruded sectional strip of steel, hardened aluminium or some other light-metal material. The illustrated design of the frame section 30 having an inwardly-direct¬ ed clamping flange 31 results in high torsional rigidity. The safety window will then be clamped between the clamping flange 31 and a frame 32 arranged on the outside. In the illustrated embodiment, the frame 32 consists of an extruded metal section 33, e.g. of aluminium or some other light-metal material, and at least one frame strip mem¬ ber 34 of high-strength material, preferably high-strength steel mate- rial, inserted in the metal section. The corners of the frame have been reinforced by there welding together the frame strip members 34 to angles, making more difficult any attempts to break them away. The joints between the frame strip members 34 are placed at the centre of the vertical or horizontal side of the frame 32 in order to facilitate mounting of the metal section 33. The frame strip member 34 is inserted in the metal section 33 with a view to bridging the joint, thus increasing the strength of the frame 32. In the illustrated embodi¬ ment, the metal section 33 is a C-section having an undercut groove 35 for accommodating the frame strip member 34, fixing screws 36 being inserted through holes in the frame section 30 and the mount¬ ing section 27 and screwed into threaded holes in the frame strip member 34. In order to provide thermal insulation and counteract the emergence of cold bridges round the safety window, two extruded decoration strips 37 and 38 of light metal are attached to the frame section 30, and an insulating material 39 is provided between the decoration strips and the frame section. In customary fashion, layers 40, 41 of jointing mastic and a cover strip 42 have been provided. A sticky sealing material 43 is, in conventional manner, provid¬ ed between the safety window and, respectively, the clamping flange 31 and the frame 32. DESCRIPTION OF AN EMBODIMENT The safety window of this embodiment is of the type shown in the drawing and thus includes two laminated glass panels 11, 12. Counting from the outside (from the right in the drawing), the outer or front laminated glass panel 11 consists of one 4-mm-thick float glass sheet, one 1.5-mm-thick binder layer of polyvinyl butyrate, three 4-mm-thick polycarbonate sheets, and one 4-mm-thick float glass sheet. The polycarbonate sheets and the inner float glass sheet are laminated with one another by means of a thin layer of epoxy adhesive, while the polyvinyl-butyrate layer serves as binder layer between the outer float glass sheet and the outer polycarbonate sheet. With such a construction, the outer laminated glass panel 11 has a thickness of 25 mm. Counting from the outside (from the right in the drawing), the inner or rear laminated glass panel 12 consists of one 4-mm-thick float glass sheet, one 8-mm-thick polycarbonate sheet, one 6-mm- thick polycarbonate sheet, one 4-mm-thick float glass sheet, one 6-mm-thick polycarbonate sheet, and one 4-mm-thick float glass sheet. The different sheets are laminated with one another by means of a thin layer of epoxy adhesive. With such a construction, the inner laminated glass panel 12 has a thickness of 38 mm. Between the two laminated glass panels 11, 12, there is an air gap of 15 mm, which is hermetically sealed by means of a circumfe¬ rential strip of aluminium section, which is open inwards towards the air gap and contains a drying agent. The entire safety window conse- quently has a thickness of about 78 mm. The test shootings accounted for below involved safety windows of the above construction, which measured 60 x 60 cm. In the test shootings, the safety windows were placed at a 90° angle to the firing line. The shot was standing 10 m from the safety window and fired 3 shots. The distance between the points of impact was about 15 cm. TEST SHOOTING A Three shots (7.62 mm live cartridge 10, muzzle velocity 820 m/sec.) were fired with an automatic carbine Ak4 at the 25-mm- thick laminated glass panel of the safety window. No bullet fragments penetrated to the back of the safety window. All the bullets stopped in the rear 38-mm-thick laminated glass panel, approximately in the rear 6-mm-thick polycarbonate sheet. The entry holes in the outer 25-mm-thick laminated glass panel "self-healed", and a nail having a diameter of 2 mm could not be driven into the entry holes by hand. The rear glass sheet in the 38-mm-thick laminated glass panel of the safety window became mealy over a surface that had a diameter of about 1 dm. Test shooting after turning the safety window, such that the 38-mm-thick laminated glass panel faced the shot, yielded the same results. TEST SHOOTING B Test shooting A was repeated, but this time the weapon was an automatic carbine Ak5 and the ammunition consisted of 5.56 mm live cartridge 5 having a muzzle velocity of 930 m/sec. Neither in this case did any bullet fragments penetrate to the back of the safety window. All the bullets stopped in the rear polycar¬ bonate sheet. The entry holes in the outer 25-mm-thick laminated glass panel "self-healed", and a nail having a diameter of 2 mm could not be driven into the entry holes by hand. The rear glass sheet in the 38-mm-thick laminated glass panel of the safety window became mealy over a surface that had a diameter of about 1 dm. Test shooting after turning the safety window, such that the 38-mm-thick laminated glass panel faced the shot, yielded the same result. TEST SHOOTING C Test shooting A was repeated, but this time the weapon was a rifle of the make Varberger and the ammunition consisted of Cal. 338 Winchester Magnum Lead point 16.2 g having a muzzle velocity of 835 m/sec. This test shooting yielded the same results as did test shootings A and B, excepting that the entry hole in the first 25-mm-thick laminated glass panel had a diameter of 6 mm. The rear glass sheet in the 38-mm-thick laminated glass panel of the safety window became mealy over a surface that had a diameter of about 2 dm. Test shooting after turning the safety window, such that the 38-mm-thick laminated glass panel faced the shot, yielded the same results. TEST SHOOTING D Test shooting A was repeated, but this time the weapon was -a rifle of the make Varberger and the an: unition consisted of Cal. 375 H & H Magnum Lead point 19.54 g having a muzzle velocity of 835 m/sec. This test shooting yielded the same results as did test shootings A and B, excepting that the entry hole in the first 25-mm-thick laminated glass panel had a diameter of 6 mm. The rear glass sheet in the 38-mm-thick laminated glass panel of the safety window became mealy over a surface that had a diameter of about 2 dm. Test shooting after turning the safety window, such that the 38-mm-thick laminated glass panel faced the shot, yielded the same results. STANDARD-HOLE-CUTTING TESTS INVOLVING HAND TOOLS These tests were carried out by the Swedish Theft-Prevention Association according to Swedish Standards SS 3492, 2nd Ed., Test with Hand Tools, Sec. 5, to provide a basis for a specification of the requirements, Sec. 4.1, 4th paragraph. In order for a safety window to make it to the highest safety class, it has to take more than 10 min. to make a standard hole measuring 100 x 100 mm in the glass panel. In the tests, two experienced experts were allowed to operate after an unlimited time of preparations. The required resistance time of at least 10 min. applies to every subtest and is not a total time for a whole glass panel. This means that one may test several areas or points where weaknesses may be found, such as the centre, the outer edges or the corners of the glass panel, as well as the attachment of the glass panel. Thus, the resistance time for each subtest must be at least 10 min. ATTEMPTED BURGLARY A The safety window used was of the same construction as the windows subjected to the test shootings. In this attempted burglary, one tried to make a standard hole measuring 100 x 100 mm. The mode of procedure and the results ap¬ pear from Table 1 below. With this procedure, it took 15 min. 38 sec. of working before the standard hole gauge could be inserted through the hole, which measured about 105 x 120 mm. ATTEMPTED BURGLARY B The safety window used was of the same construction as the windows subjected to the trial shootings and attempted burglary A. In attempted burglary B, one used a slightly different approach when making the standard hole measuring 100 x 100 mm. The mode of procedure and the results appear from Table 2 below. With this procedure, it took 15 min. 7 sec. of working until the standard hole gauge could be inserted through the hole, which measured about 120 x 100 mm. COMPARISON - ATTEMPTED BURGLARY C This comparative test involved a commercially available safety window composed of eight laminated flat glass sheets and having a total thickness of 39 mm (the make VEGLA from St Gobain). The mode of procedure and the results appear from Table 3 below. The cut hole measured about 130 x 130 mm. As appears from the results, it took much less than 10 min. to make the standard hole. TABLE 1 Attack Tool Total time Crushing of glass outer layer Sledge, pointed chisel, 40 sec. chisel retainer Drilling through outer layer Drilling machine, drill φ 10 1 min. 26 sec. Crushing of glass inner layer Sledge, pointed chisel, 2 min.50 sec. chisel retainer Drilling through both glasses Drilling machine, drill φ 10 7 min.25 sec. and milling between the holes Breaking-away of outer layer Jemmy 7 min.40 sec. Further drilling Drilling machine 8 min.15 sec. Breaking Jemmy 8 min.25 sec. Smashing towards inner Sledge 8 min.40 sec. layer Drilling towards inner layer Drilling machine, drill φ 10 9 min.55 sec. Smashing towards inner Sledge 10 min. 15 sec. layer Further drilling Drilling machine, drill φ 10 11 min. 3 sec. Crushing of glass inner Sledge, pointed chisel, 11 min.55 sec. layer chisel retainer Drilling towards inner Drilling machine, drill φ 10 12 min.45 sec. layer Cutting between holes in Sledge, pipe wrench, 12 min.55 sec. inner layer slot chisel Drilling towards inner Drilling machine, drill φ 10 layer 13min.20 sec. Cutting between holes in Hand sledge, pipe wrench, 13 min.55 sec. inner layer slot chisel Drilling towards inner Drilling machine, drill φ 10 14 min. 45 sec. layer Smashing towards Sledge 15 min. 38 sec. inner layer TABLE 2 Attack Tool Total time Crushing of glass outer layer Sledge, pointed chisel, 25 sec. chisel retainer Drilling through outer layer Drilling machine, drill φ 10 2 min. 55 sec. 23 holes Crushing of glass inner layer Sledge, pointed chisel, 3 min. 41 sec. chisel retainer Drilling through inner layer Drilling machine, drill φ 10 7 min. 5 sec. 23 holes Cutting between holes in Sledge, slot chisel, 7 min. 25 sec. outer layer pipe wrench Milling between holes in Drilling machine, drill φ 10 9 min. 15 sec. outer layer Cutting between holes in Sledge, axe 10 min 10 sec. outer layer Breaking-away of outer layer Jemmy 10 min 32 sec. Cutting between holes Sledge, axe 12 min 22 sec. Further drilling in inner Drilling machine, drill φ 10 13 min 5 sec. layer Cutting between holes in Sledge, slot chisel, 13 min.37 sec. inner layer pipe wrench Cutting between holes in Sledge, axe 14 min. 12 sec. inner layer Further drilling in inner Drilling machine, drill φ 10 14 min. 5 sec. layer Smashing of inner layer Sledge 15 min. 7 sec. TABLE 3 Attack Tool Total time Cutting of three sides of Sledge, chisel retainer, 2 min. 15 sec door pointed chisel Drilling and milling Drilling machine, drill φ 10 3 min. 20 sec. Smashing of door Sledge 3 min. 31 sec. COMPARISON - ATTEMPTED BURGLARY D This test involved a laminated glass panel of the same construc¬ tion as the thick, rear laminated glass panel in the safety window according to the invention. The laminated glass panel tested thus had the same structure as the rear panel 12 in the embodiment described above. The mode of procedure and the results appear from Table 4 below. The standard hole gauge measuring 100 x 100 mm could be inserted through the hole after 7 min. and 12 sec. TABLE 4 Attack Tool Total time Crushing of glass before Sledge, chisel retainer, 20 sec. drilling pointed chisel Drilling through plastic Drilling machine, drill φ 10 2 min. 25 sec. layer Crushing of glass Sledge, chisel retainer, 3 min. 25 sec. pointed chisel Drilling through plastic Drilling machine, drill φ 10 5 min. 50 sec. layer Smashing attempt at Sledge 6 min. opening made Milling between holes Drilling machine, drill φ 13 6 min. 25 sec. Smashing of opening Sledge 7 min 12 sec.

Claims: CLAIMS 1. A safety window comprising a number of successive glass and polycarbonate sheets (15-19, 21-26) and being designed as a glass sheet unit (10), ch ara c te ri s e d in that the glass sheet unit (10) comprises at least two spaced-apart laminated glass panels (11, 12) which consist of joined glass and polycarbonate sheets (15-19, 21-26) and which each comprise at least two glass sheets (15, 16, 21-23) and three polycarbonate sheets (17-19, 24-26), these sheets being so laminated with each other that the two outer surfaces of each laminated glass panel (11, 12) are formed of glass sheets (15, 16, 21, 23). 2. A safety window as set forth in claim 1, c h arac te r - i s e d in that a transparent layer (20) of elastomeric material, pre- ferably polyurethane, is inserted in at least one of the laminated glass panels (11, 12). 3. A safety window as set forth in claim lor2, c h ar ac ¬ te ri s e d in that the glass and polycarbonate sheets (15-19, 21-26) forming part of the laminated glass panels (11, 12) are lami- nated with one another over their entire mutually facing sides, use being made of a binder layer of epoxy adhesive, polyurethane or poly- vinyl butyrate. 4. A safety window as set forth in claim 1,2 or 3, c h a r ¬ ac te ri s e d in that it is inserted in an assembly unit compris- ing a mounting structure (27), the glass sheet unit (10) being clamped between a circumferential frame (33, 34) of high-strength material, preferably steel, which is applied against the outside of the mounting structure (27), and a circumferential torsionally rigid frame section (30) fixed on the inside of the mounting structure. 5. A safety window as set forth in claim 4, c h ar a c te r ¬ ise d in that the circumferential frame section (30) at its inner edge is provided with an inwardly-directed clamping flange (31) which is adapted to form a mounting flange for the glass sheet unit (10). 6. A safety window as set forth in claim 4 or 5, c h arac - te ri s e d in that the frame section (30) and the frame (32) are screwed together to clamp the glass sheet unit (10) between them.

Inventors: JOHANSSON JERZY KRYSZOF, JOHANSSON, JERZY, KRYSZOF
Applicants: JOHANSSON JERZY KRYSZOF, JOHANSSON, JERZY, KRYSZOF
Application year: 1994
Main classification: C03C27
IPC codes: B32B17, B32B27, C03C27, E06B5, F41H5